The real JD 4520: Compression Issues

[Hay maker2]

1969 John Deere 4520 with the correct 4520 engine (rear mount injection pump, JDB). I have owned this tractor for 3 years and have been slowly fixing it up. I have a starting issue and the compression is low. I have to use either, plug it in on a 65-degree day, or crank the snot out of it on a 90-degree day to get to start. Per the manual the compression should be between 385 – 410PSI @ 215 – 245RPM

I initially pulled all the injectors and tested compression and on average, each piston was about 300PSI. I did an in-frame overhaul and when I got the head off, the sleeves looked excellent, no wear marks or anything to my surprise. I pulled one sleeve just because. These were manufactured by Clevit and I did some research and was able to verify that they are correct for the application. While researching I located a set of NOS Cleveite piston kits a couple of hours from me, so I bought them for little to nothing and installed all of them for peace of mind. At the same time, I sent the head to my machinist, and he said it was cracked. It took some time, but I found a refurbished head and reassembled everything with a JD Head gasket. To my surprise I have the same issue, low compression (300PSI). I even put on my dyno, and it holds 125HP

I blamed the Clevite piston kits and sucked it up and bought the Reliance High Compression kits (I have had excellent success with these High Compression kits). I installed these and sent my refurbished head to my machinist and he said that the seats and valves were misaligned. He repaired this and I reassembled everything and still have low compression, 300PSI.

Currently I have the basic engine back together, but the coolant pump and hydraulic pump are not connected for testing. Oil in the pan and no water in the engine. Compression is still at 300PSI.

I have done the following:

Valves are set per the manual 0.018” intake and 0.020” exhaust. I have checked these several timed and even gapped these to 0.020” and 0.022” with no luck.

Before placing the head on I brought piston #1 to TDC using a dial indicator, this is within 0.001” of true TDC. The TDC mark on the fly wheel is about 3/16” off, but per my service bulletins it can be off as much as ¼’ with no effects.

I even timed everything based on TDC on the flywheel to the casted line in the inspection window with no change in performance.

Timing marks on cam gears are aligned along with TDC on the piston and flywheel.

Injection pump is timed.

Cranking RPM is averaging 225RPM (coolant & Hydraulic pump not hooked up) with photo tachometer

I have used 2 different compression testers, and both are within 5-10PSI

Suggestions?
Thanks

 

[Hay maker2]

Correction.
Its a 1969

 

[matthies]

Can you try a different starter, maybe this one is tired. Cables and clean grounds?

 

[Hay maker2]

Can you try a different starter, maybe this one is tired. Cables and clean grounds?

Plan is to swap starters with my 4020 later this week.

 

[used red MN]

First how much do you trust your cylinder head shop? Do they do a lot of tractor and diesel work? It sounds like you have discussed your problem with them. Any good cylinder head shop worth their salt should be aware of the specs for proper final installed valve height of the valve head in comparison to the cylinder head surface. When they drop down to far the compression drops.
The other thing I would question is the cam correct? I don’t know how many cams would “fit” in this engine but possibly be the wrong one. Since it has the drive gear for the injection pump that probably limits the possibility of a mistake. Have you had the cam out and checked the part number? I would at the very least check it for proper timing by using the number 6 cylinder valve “rock” position. That is the exhaust valve is closing and the intake is opening. When those valves are open the same amount your crankshaft should be within 5 degrees of the TDC mark. If it is not “something is smelling in Denmark”

 

[Hay maker2]

First how much do you trust your cylinder head shop? Do they do a lot of tractor and diesel work? It sounds like you have discussed your problem with them. Any good cylinder head shop worth their salt should be aware of the specs for proper final installed valve height of the valve head in comparison to the cylinder head surface. When they drop down to far the compression drops.
The other thing I would question is the cam correct? I don’t know how many cams would “fit” in this engine but possibly be the wrong one. Since it has the drive gear for the injection pump that probably limits the possibility of a mistake. Have you had the cam out and checked the part number? I would at the very least check it for proper timing by using the number 6 cylinder valve “rock” position. That is the exhaust valve is closing and the intake is opening. When those valves are open the same amount your crankshaft should be within 5 degrees of the TDC mark. If it is not “something is smelling in Denmark”

As for my head shop, he does a lot of work for many farmers and repair shops in the area. He has done 5 or 6 heads for me over the past several years. When I drop any head off I always include the technical manual as this provides the specifications of the mins and maxs.

I have not pulled the cam, but I also feel that this will be one of the next things to verify. Based on the parts book, at minimum the cam-gear has the correct casting number on it. Maybe the cam gear shared the woodruff key and is partially out of time or maybe the cam is twisted. The painful part is that I would need to pull a head and yet another head gasket in order to get the cam out.

I will check the intake & exhaust valves on piston #6 to see if the intake is opening and the exhaust is closing.

 

[used red MN]

As for my head shop, he does a lot of work for many farmers and repair shops in the area. He has done 5 or 6 heads for me over the past several years. When I drop any head off I always include the technical manual as this provides the specifications of the mins and maxs.

I have not pulled the cam, but I also feel that this will be one of the next things to verify. Based on the parts book, at minimum the cam-gear has the correct casting number on it. Maybe the cam gear shared the woodruff key and is partially out of time or maybe the cam is twisted. The painful part is that I would need to pull a head and yet another head gasket in order to get the cam out.

I will check the intake & exhaust valves on piston #6 to see if the intake is opening and the exhaust is closing.

Hopefully you realize that the valve “rock” event of #6 only happens when #1 is at TDC compression. The cam timing can also be checked on the rock event for #1 cylinder but at that point #6 is at TDC compression.
Editing to add: The front gear train is timed per illustrations in the service manual. Sometimes the position of a key way or setting the engine at TDC is misunderstood as being correct. I’m not sure how this applies to this particular Deere engine as far as how easily such items could get confused. I would be surprised if there is an actual cam timing issue since you say the tractor will dyno at rated hp, but you are trying to diagnose why the compression won’t test at spec.

 

[Hay maker2]

I swapped starters form my 4020, I have the same compression with similar cranking RPM's

As for checking the "rock" on piston #6 when piston #1 is at TDC compression: I used 2 dial indictors to follow both the intake and exhaust rocker arms. This appears to be correct. As when the exhaust is just about closed, the intake is starting to open within a few degrees of rotation.

 

[rockcreek4630]

Did you put some oil in the cylinders and see if that helps.

 

[rustred]

If you’re at 300 psi. And u have new pistons and rings , it’s kinda obvious that your valve recession is below factory spec’s. New valves and seats are usually good for one regrind depending on wear. So if your valves are recessed too far u are loosing compression and naturally it will be a hard starter. Plus timing must be at factory spec. Plus injectors spraying properly.plus proper cranking speed And do not put oil in diesel cylinders. Plus u say the head is refurbished. That don’t mean much unless a person visually inspects the job and measures the valve recession. So find a valve recession spec and take it from there.

 

[Powered By IH]

Valve recession spec for the 4520:

 

[rustred]

Valve recession spec for the 4520:
View attachment 141009

You found it !

 

[Powered By IH]

You found it !

I'll find anything if ya pay me enough...

Seriously though, if anyone needs a spec shoot me a message and I'll see if I can find it in my books.

 

[rustred]

Here is my crazy thinking. Say new compression is 400 psi. Pull out 2 fifty cent coins imitating the valve face and seat wear from the combustion chamber and that will
Drop your compression down due to more combustion area. Someplace I heard or had how much it will drop for so many thou. Of valve recession. On this engine you’re only allowed .014 wear per valve and seat so that’s very little. Means replace seats on every valve job basically. Gotta squish that air pretty tight to get it hot enough to ignite that diesel.

 

[buickanddeere]

Valves are sunk in the head .
Front pump needs a de-stroker
Needs a 5Kw starter motor
Cam shaft is both worn and is out of time .
Injection timing is probably not advanced far enough .

 

[brendonh]

Just curious here, how far do you pull the throttle when starting?

For me, it was all the way. Simulates the starting fuel setting of a bosch inline pump of later machines.
In my experience, Grandpa's 5010's, both early and late 4020's and my 4230 all need that max fuel throttle setting to wake up easier.

Also agree with buickanddeere. Nobody ever checks valve recession very much on these old heads even after a regrind. Neither did I. Mostly because you could see it. The valves wouldn't have any margin left, so they would get replaced. If the seats took that much cutting to get cleaned up and sat low, those got replaced. I don't know this, but I rather doubt a usable seat and or a usable valve would recess in the head that bad to cause super low compression by itself, and across all cylinders at the same time? Ok... well... maybe...stranger things have happened..

I'm sure the cam is shot, but those are only ever changed when the oil pump won't turn anymore on these 404's. I'd bank on the pump is also out of time also.
However, none of this addresses low compression, rather ease of starting. Assuming the valves don't leak, the piston rings don't leak, there's nothing left except stroke. I doubt that anything is wrong there either.

I do know that Deere had this problem..... Starting has been an issue until the days of the 6076, when they redesigned the combustion chambers and where the top ring was on the piston. 404's were miserable when they put turbos on them. The compression was reduced on turbo engines because of the turbo. So, anything with a 404 or 466 was a miserable female dog to light off when it was 50* or less outside. Personal experience comes from 4020's, 4230, 4630 (that I grew up with) and a 4640 (also grew up with, both were my office during my school days and college). I'm wondering if the book is wrong. When we rebuilt engines in the dealership, we never, I mean no of us, even the old guys didn't ever check compression. I've never checked compression on any of them either, so I can't tell you what "actual" ever was, new or used..... They either ran good, or they didn't. Compression was checked by how much blow by we got and how much blue smoke was issued after she'd warmed up. We did things they way cause we were on the clock and the bill meter was running. Compression testing was deemed unnecessary by the elders.

My 4320 book shows the same numbers for compression as what's been listed already.
The 4640 and 4840 run in the book at 330 - 370.
Theoretical compression ratio for the 4640/4840 would be 24:1, calculated by taking atmospheric pressure on a standard day of 14.7 psi, and diving the requested psi on the compression gauge, i used 350psi. That came to : 350psi / 14.7psi = 23.8. So, the ratio, per math is 23:1. The book for the 46/4840 said the compression ratio is actually 14.9:1. Running that number, 14.7 psi * 14.9 compression ratio = 208psi. So, I'd expect a perfectly good engine in a 46 or 4840 to be at least above 208psi on the gauge. The book says 330-370psi. The difference is in all the factors the math is not considering on the given day and with the given engine along with factors of gas compression laws the simple math formula isn't looking at.

All that said, I think the compression is fine on that engine. 330 is a lot closer to measured in this instance. I understand its a 404 vs 466, but I don't put much stock in that difference since both engines basically the same in combustion chamber design, and both are Deere engines. A compression number from a 4620 or a 4430 would be usefull since both of those engines are exactly the same as the 4520 in question here.

I would give anything to set down at my old service manager computer and search the DTAC solutions for starting and/or compression related solutions on these. I'm sure there are suggestions in there. Alas, I never had reason to do that search when I was a service manager, so I don't remember any of them.

Sorry all for the rambling. Just trying to think this out a little more..

Thanks~
Brendon

 

[Fritz Maurer]

There was a hard start topic on Deeres maybe 6 months ago.... it had some screwball injector pump that had to be set just so for a cold start.... after many pages of replies , this became evident and there was no more trouble .

This gentleman had installed new S/P groups as well, and still had a hard starter.

Also in this same thread, a number of guys were adamant about the valve recession being the problem. It wasn't.

 

[brendonh]

There was a hard start topic on Deeres maybe 6 months ago.... it had some screwball injector pump that had to be set just so for a cold start.... after many pages of replies , this became evident and there was no more trouble .

This gentleman had installed new S/P groups as well, and still had a hard starter.

That odd ball pump was the first generation Bosch pumps that used the kill cable to reset the starting fuel system. If you killed it in the field, there was no way it would relight again before you cycled the kill cable in the cab. That action reset the plunger that allowed the rack to move into starting delivery setting. Most of the time the linkage that does that is so worn out, it won't move the plunger, so down you go, slip your hand between the pump and block, burn it, flip the lever manually, then it'll relight. Bosch did away with that system and used the aneroid to move the plunger and that system worked lots better. You still had to cycle the kill cable to reset the system, but the linkages never wore out.

 

[rockcreek4630]

Just curious here, how far do you pull the throttle when starting?

For me, it was all the way. Simulates the starting fuel setting of a bosch inline pump of later machines.
In my experience, Grandpa's 5010's, both early and late 4020's and my 4230 all need that max fuel throttle setting to wake up easier.

Also agree with buickanddeere. Nobody ever checks valve recession very much on these old heads even after a regrind. Neither did I. Mostly because you could see it. The valves wouldn't have any margin left, so they would get replaced. If the seats took that much cutting to get cleaned up and sat low, those got replaced. I don't know this, but I rather doubt a usable seat and or a usable valve would recess in the head that bad to cause super low compression by itself, and across all cylinders at the same time? Ok... well... maybe...stranger things have happened..

I'm sure the cam is shot, but those are only ever changed when the oil pump won't turn anymore on these 404's. I'd bank on the pump is also out of time also.
However, none of this addresses low compression, rather ease of starting. Assuming the valves don't leak, the piston rings don't leak, there's nothing left except stroke. I doubt that anything is wrong there either.

I do know that Deere had this problem..... Starting has been an issue until the days of the 6076, when they redesigned the combustion chambers and where the top ring was on the piston. 404's were miserable when they put turbos on them. The compression was reduced on turbo engines because of the turbo. So, anything with a 404 or 466 was a miserable female dog to light off when it was 50* or less outside. Personal experience comes from 4020's, 4230, 4630 (that I grew up with) and a 4640 (also grew up with, both were my office during my school days and college). I'm wondering if the book is wrong. When we rebuilt engines in the dealership, we never, I mean no of us, even the old guys didn't ever check compression. I've never checked compression on any of them either, so I can't tell you what "actual" ever was, new or used..... They either ran good, or they didn't. Compression was checked by how much blow by we got and how much blue smoke was issued after she'd warmed up. We did things they way cause we were on the clock and the bill meter was running. Compression testing was deemed unnecessary by the elders.

My 4320 book shows the same numbers for compression as what's been listed already.
The 4640 and 4840 run in the book at 330 - 370.
Theoretical compression ratio for the 4640/4840 would be 24:1, calculated by taking atmospheric pressure on a standard day of 14.7 psi, and diving the requested psi on the compression gauge, i used 350psi. That came to : 350psi / 14.7psi = 23.8. So, the ratio, per math is 23:1. The book for the 46/4840 said the compression ratio is actually 14.9:1. Running that number, 14.7 psi * 14.9 compression ratio = 208psi. So, I'd expect a perfectly good engine in a 46 or 4840 to be at least above 208psi on the gauge. The book says 330-370psi. The difference is in all the factors the math is not considering on the given day and with the given engine along with factors of gas compression laws the simple math formula isn't looking at.

All that said, I think the compression is fine on that engine. 330 is a lot closer to measured in this instance. I understand its a 404 vs 466, but I don't put much stock in that difference since both engines basically the same in combustion chamber design, and both are Deere engines. A compression number from a 4620 or a 4430 would be usefull since both of those engines are exactly the same as the 4520 in question here.

I would give anything to set down at my old service manager computer and search the DTAC solutions for starting and/or compression related solutions on these. I'm sure there are suggestions in there. Alas, I never had reason to do that search when I was a service manager, so I don't remember any of them.

Sorry all for the rambling. Just trying to think this out a little more..

Thanks~
Brendon

From 4430 4630 book pic won't load.

 

[rockcreek4630]

From 4430 4630 book